SIP entities, such as SIP redirect servers, SIP proxy servers, and IP multimedia subsystem (IMS) entities, communicate using the SIP protocol. SIP entities can be used to establish communications sessions between users in networks that use the SIP protocol. One example of a network that uses the SIP protocol is an IMS network. IMS network is a network through which multimedia communications can be established between users and between users and applications. In the IMS network, SIP is the signaling protocol used to establish communication sessions. The entities involved in establishing a communication session in an IMS network include call session control functions (CSCFs) that communicate with each other using the SIP protocol.
One problem with the conventional call setup scenarios with SIP entities, including SIP entities in an IMS network, occurs when a call session control function becomes unavailable. When an originating call session control function receives a request to establish a communication, the originating call session control function may attempt to contact a terminating call session control function associated with the called party. If the terminating call session control function is unavailable, the originating call session control function may be required to wait for a timeout period defined by the SIP protocol before attempting to contact an alternate call session control function. The originating call session control function typically does not store operational status information for other call session control functions with which it communicates. As a result, when a second communication setup request arrives at the originating call session control function, the originating call session control function may again attempt to contact the failed call session control function. Repeated attempts to contact a failed call session control function and the associated time out periods waste resources of the originating call session control function and delay call establishment.
Commonly-assigned, co-pending U.S. patent application Ser. No. 11/510,284, filed on Aug. 25, 2006, the disclosure of which is incorporated herein by reference in its entirety, discloses methods and systems by which a SIP server can obtain and store operational status information for a terminating SIP server to avoid at least some of the aforementioned problems. However, neither SIP nor IMS provides a mechanism for distributing SIP operational status information among SIP servers or IMS nodes. As a result, in order to obtain Application or higher layer communications network signaling entity operational status, each SIP originating server would be required to test the operational status of each terminating SIP server using the methods and systems described in the referenced patent application.
The problem of obtaining and distributing operational status information among SIP entities is not limited to obtaining and distributing operational status information regarding SIP servers. For example, it may be desirable to obtain and distribute operational status information regarding other application and higher layer entities, such as presence applications and ENUM applications, among SIP entities. Using current methods, each SIP entity that desires or needs to communicate with an application or higher layer communications network signaling entity would be required to individually test each application or higher layer communications network signaling entity to determine its operational status, resulting in wasting of SIP node resources and network bandwidth.
Accordingly, in light of these difficulties, there exists a need for improved methods, systems, and computer program products for distributing application or higher layer communications network signaling entity operational status information among SIP entities.